The long-range goal of this project is to understand the role of serum hormone binding proteins in the regulation of normal physiologic processes and in the pathophysiology of various human disease states. A unique solid phase method for characterizing ligand interactions with testosterone-binding globulin and corticosteroid-binding globulin under equilibrium conditions at physiologic pH and temperature has been developed. Using a computer program, the plasma distribution of 21 endogenous circulating steroids has been computed for men, cycling women, and pregnant women. The physiological significance of the interaction of 70 drugs with these carrier proteins has been assessed. Future research will initiate exploration of the biological significance of hormone transport proteins.